The present invention relates to a method of cylinder shut-off in an internal combustion engine, in particular of a vehicle, corresponding to a shut-off program.
Furthermore, the present invention relates to a device for cylinder shut-off in an internal combustion engine, in particular of a motor vehicle, using a control unit which is in effective operational contact with the cylinders of the internal combustion engine, which has a monitoring unit, a knock regulating unit and a fuel injector shut-off unit.
Conventionally, cylinder shut-off in an internal combustion engine, in particular of a vehicle, corresponds to a predefined shut-off program. Here, a shut-off of the corresponding fuel injectors for selected cylinders takes place, so that fuel is no longer supplied to the corresponding cylinder, i.e., combustion chamber. Thus, no combustion occurs in the cylinders shut off in this way. A fuel injector shut-off, i.e., a cylinder shut-off, may be provided here for the following reasons:
to implement a reduction in torque, which is necessary during interventions of an acceleration-spin control (ASR) or an antilock-braking system (ABS), or to create a fuel-optimizing reserve of torque for rapid torque build-up;
for torque-neutral reduction of throttle losses under partial load in order to achieve greater overall efficiency;
to protect the catalytic converter when combustion is interrupted.
In all of the cases identified above, the cylinders are shut off by using a masking pattern which is fixedly preset in the first two cases and allows free shut-off of one or more cylinders, while in the third case the masking pattern is preset by a misfire recognition system. Disadvantageously, with cylinder shut-off using a masking pattern in one or more of the cases named above, degradation of engine efficiency results.
In accordance with an example embodiment of the present invention, in a method of cylinder shut-off in an internal combustion engine, in particular of a vehicle, a shut-off program shuts the cylinders off by coordinating the shut-off program with knock regulation of the individual cylinders of the internal combustion engine. Using a conventional system of knock regulation of individual cylinders, each cylinder of the internal combustion engine is operated at optimum efficiency, i.e., at the knock limit, under consideration of various operating conditions. Because variation occurs between individual cylinders in regard to compression, charge, thermal load, air ratio value (lambda) and other operating parameters, the margin between the real knock limit and the theoretical optimal efficiency, and thus also the ignition angle efficiency, varies by individual cylinder. Furthermore, knock regulation of individual cylinders allows activation of a knock regulation/guide cylinder function, whereby cylinders having poor or no knock recognition are guided by the other cylinders of the internal combustion engine which have good knock recognition. The leading cylinders are also referred to as guide cylinders. Thus, the knock regulation of individual cylinders provides data or information which may be important for achieving efficiency-optimized cylinder shut-off. By coordinating cylinder shut-off and knock regulation by individual cylinders, it is possible to ensure in a reliable way that, in case of need, those cylinders will be shut off which are working at relatively low efficiency and/or are being operated as guided cylinders. Cylinder shut-off which significantly reduces engine efficiency, in the form of shutting off the cylinders working at high efficiency and/or the guide cylinders, is, thus, possibly prevented under consideration of data from the system of knock regulation by individual cylinders which is relevant to shut-off.
According to one example embodiment, a cylinder-specific ignition angle retardation value is used as a cylinder shut-off criterion. By using the cylinder-specific ignition angle retardation value, it is possible to determine the ignition angle efficiency of the respective cylinder. It is thus possible, by appropriate selection of the cylinder to be shut off, i.e., the cylinder with the greatest ignition angle retardation at the moment and thus having the relatively lowest ignition angle efficiency, to achieve efficiency-optimized cylinder shut-off.
According to another example embodiment, a classification of the cylinders in terms of a knock regulation-guide cylinder function is used as a cylinder shut-off criterion. When a knock regulation-guide cylinder function is activated the guided cylinders always exhibit ignition angle retardation quantitatively greater than or equal to the guide cylinders. It is thus, possible, through classification, to reliably prevent shut-off of a guide cylinder before a guided cylinder which has not yet been shut off.
The cylinders may be shut off corresponding to a hierarchy according to the classification of the cylinders. Through creation of a hierarchy corresponding to predetermined ranking criteria, it is possible to ensure automatic, efficiency-optimized cylinder shut-off in a particularly effective manner, using, for example, a control unit. The hierarchy may be organized here, for example, as a bit matrix, which advantageously allows rapid access to data stored in it and thus makes particularly effective automatic cylinder shut-off possible.
Advantageously, the cylinders may be assigned according to the hierarchy, with decreasing cylinder shut-off priority, to the priority groups: guided cylinders, neutral cylinders and guide cylinders. This allows efficiency-optimized cylinder shut-off, under which, when necessary, the cylinders defined by the knock regulation system as guided cylinders are shut off first, and only after all of the guided cylinders are shut off are the neutral cylinders (neither guided nor guide cylinders) released for shut-off. Only under the condition that all of the guided and neutral cylinders have already been shut off is shut-off of a guide cylinder allowed in the event of need. In this way, avoidable degradations of engine efficiency due to unfavorable cylinder shut-off are prevented, so that the internal combustion engine is operated at the best ignition angle efficiency possible under the existing conditions. This results in a corresponding reduction in fuel consumption and a lowering of exhaust gas emissions during operation of the internal combustion engine.
According to another example embodiment of the present invention, the specific fuel consumption of the respective cylinder is used as a shut-off criterion. The specific fuel consumption for a cylinder may be calculated in a precise manner from the respective injection time and the respective cylinder moment, which in turn may be determinable from the measured segment time. Thus, the specific fuel consumption is also suitable as a cylinder shut-off criterion, as an alternative to the ignition angle.
Advantageously, the cylinder shut-off may take place in the form of a shut-off of fuel injectors belonging to a cylinder which is to be shut off. This enables particularly rapid, reliable and precisely controllable cylinder shut-off.
The device according to the example embodiment of the present invention is characterized by the fact that the fuel injector shut-off unit is operationally linked to the knock regulating unit to achieve coordinated cylinder shut-off. By using a device of this design, it is possible to execute a method of cylinder shut-off in an internal combustion engine while achieving the forenamed advantages.
According to an example embodiment, the fuel injector shut-off unit is provided with a memory medium for storing a cylinder shut-off program. This permits central storage of a control program created according to one or possibly more cylinder shut-off criteria for efficiency-optimized cylinder shut-off.